Weird Transmission Slipping
 

Not sure what's going on but would appreciate thoughts. For several months I'd slip going from first to second (I think) but only when aggressively mashing gas pedal to floor. Very repeatable. I'd NEVER slip if driving normal, just easing my way up to speed. This would also sometimes happen when mashing gas down to pass someone - say trying to quickly go to 80 from 60. Not always repeatable, and would also never happen if increasing speed more gradually.

Symptom - engine would race, RPM's would soar, but speed wouldn't budge. I'd let of gas and transmission would 'catch', with a somewhat violent clunk. Never seemed to get worse, symptoms stayed constant.

Yesterday I added 28 oz bottle of Lucas Transmission Slip. Fluid level was low before I added, reading down in the Cold range when car running and transmission hot. Now reads in the middle of Hot range.

New symptoms post additive: I've completely eliminated the slipping on the low end. But now the slipping is worse on the higher speeds. Very repeatable, going from 40-60 with pedal mashed down. Doesn't happen if less aggressive but more annoying than what I had before.

Thoughts on cause and fix. A little more fluid? I'm encouraged that I've eliminated the low speed slipping and changed the symptoms, maybe fluid level/viscosity related?

Should have mentioned - 2009 base model (5 cylinder). 135k miles, automatic. Symptoms mentioned before adding Lucas started maybe 25-30k miles ago. No codes thrown.

id do a compleat drain and fill and filter,and stop mashing the gas, im in year 8 driving h3;s. have not needed to mash the gas yet...routine flooring the gas will take its toll on the tranny and other driveline parts.

Thanks Happythree. I don't normally abuse my H3, but when trying to pass or merge onto highway it is sometimes necessary to "punch it". Can be a little annoying, and sometimes dangerous, when nothing happens. I can try what you suggest, I'd like a few more opinions. This thing has been a complete POS from Day 1, I had $8-10K in repairs done under extended and powertrain warranties. That included a new transfer case (complete) at 85K miles, along with new clutch(s) after that. And a bunch of other smaller stuff. Been good since, other than this slipping issue, that started after both warranties expired. I want to trade it in but want to deal with this problem first - a friend runs the Jeep dealership where this is going.

At 135K miles you are approaching rebuild territory. If you are experience slipping, that is Mr. Rebuild's calling card.

When was the last time you changed the trans fluid and filter?

Over-filing is never good, regardless if you think it is liquid fix in a bottle.

replaced ours at 115k miles, cheaper to replace with a GM reman than to rebuild, trans cost 1300.00 plus labor, now a 100k mile warranty

was that done by a dealer?

However, when you rebuild, you can choose what to use and make it bullet proof instead of just getting another ho hum stock trans.

The 4L60E can be built to handle 1000HP.... yes that is 1000. Obviously we do not have to go that crazy with these trucks, but you can pick some key upgrade parts and practice good fluid maintenance and almost assuredly, never have to rebuild again as long as the truck lasts. :cool:

true they can be built, and yes I had a GM dealer do the swap. If I get another 100k I will be happy

My tranny totally puked at 78,000 miles and it cost me big league to have it rebuilt. The builder said the H3's run too hot if you live anywhere in the mountains and routinely go over 200° when in hilly terrain. My next project will be a Tru=Cool tranny cooler